Let there be ... Light

Click here and here to view simulations of electromagnetic waves. Click here to explore a tutorial on the production of e/m waves.

Light is radiant energy transported in photons that are guided along Although we still commonly characterize light as a wave, it is actually neither a wave nor a particle. It seems to have characteristics of both. The modern view of the nature of light recognizes the dual character: Light is radiant energy transported in photons that are guided along their path by a wave field.

Light is ... This leads us to the Duality Principle: a wave when it acts like a wave a particle when it acts like a particle

Visible light is that portion of the electromagnetic spectrum which stimulates the retina of the human eye. Visible spectrum wavelengths range from about 400 nm (violet) to 760 nm (red). Light travels at about 3 x 108 m/s through empty space and slightly slower through air. Remember that for all waves, v = f.

Laws of Reflection First Law Second Law The angle of incidence, i, is equal to the angle of reflection, r. n i r Second Law The incident and reflected rays, and the normal, are coplanar.

Real Image Virtual Image Images formed by mirrors and lenses may be classified as real or virtual. Real Image formed by actual rays of converging light Virtual Image not formed by actual rays of converging light, but from where the rays of light appear to come (diverging light rays)

Plane Mirror Images 1. virtual 2. upright 3. same size as object Images formed by plane mirrors are always: 1. virtual (virtual images are always behind mirrors) 2. upright (virtual images are always upright) 3. same size as object (if the image is larger or smaller, the mirror isn’t flat) 4. front and back are reversed (some say “left and right”) 5. located as far behind the mirror as the object is in front